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Chemistry (Inorganic) > Group 7 > Flashcards

Group 7 Flashcards

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1
Q

Describe the trend in reducing abilities of halide ions

A

Reducing ability increases down the group

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2
Q

Explain the trend in reducing abilities of halide ions

A

Reducing ability increases down the group
- Ionic size increases down the group
- Shielding increases
- Attraction between outer electron and nucleus decreases
- So electron is more easily lost

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3
Q

What is the type of reaction between halide ion and concentrated H2SO4

A

Acid base reaction

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4
Q

What is the general formula for the reaction between halide ion and concentrated H2SO4

A

H2SO4 + NaX —> NaHSO4 + HX

Ionic equation:
(H+ + X - —> HX)

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5
Q

What is the observation when Br2 is formed

A

Brown/orange fumes

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6
Q

What is the observation when I2 is formed

A

Black solid/ Purple fumes

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7
Q

What is the observation when SO2 is formed

A

Pungent gas

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8
Q

What is the observation when S is formed

A

Yellow solid

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9
Q

What is the observation when H2S is formed

A

Smell of bad eggs

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10
Q

Describe the trend in electronegativity of halides

A

Decreases down the group

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11
Q

Explain the trend in electronegativity of halides

A

Decreases down the group

  • Atomic size increases
  • Shielding increases
    -Weaker attraction between nucleus and shared pair of e- of the covalent bond
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12
Q

State the trend in boiling point of the halides

A

Boiling point increases down the group

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13
Q

Explain the trend in boiling point of the halides

A

Boiling point increases down the group

  • Molecular size increases
  • Number of electrons increases
  • Van der waals forces between molecules increases
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14
Q

What is the best oxidising agent out of the halides

A

F2

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15
Q

What is the worst oxidising agent out of the halides

A

I2 (more shielding therefore worse at gaining an electron)

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16
Q

What is the best reducing agent out of the halide ions

A

I-

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17
Q

What is the worst reducing agent out of the halides

A

F-

18
Q

What is observed when Cl2 is formed?

A

Green solution

19
Q

What are the 4 main steps in testing for halide ions

A

1) Add HNO3
2) Add AgNO3
3) Add dilute NH3
4) Add concentrated NH3

20
Q

Why do we add HNO3 in the first step of identifying halide ions

A

Removes Co32- ions
(essential as Ag2CO3 is a white ppt)

21
Q

Which element is clearly identified after adding AgNO3 in the halide ion test

A

F-
(Gives a colourless solution)
(The others give white, cream and yellow)

22
Q

Which element is clearly identified after adding dilute NH3 in the halide ion test

A

Cl-
(In Cl- white ppt dissolves, Br- and I- have no visible change)

23
Q

Which element is clearly identified after adding concentrated NH3 in the halide ion test

A

Br-
(In Br- cream ppt dissolves, I- has no visible change)

24
Q

What is the test for I- ions

A

No visible change after completing all 4 steps of halide ion test

25
Q

What is the formula for the chlorate ion

A

ClO-

26
Q

What is the equation for the reaction of chlorine and water without UV light

A

Cl2 + H2O –>HCl + HClO (reversible)

Ionic:
Cl2 + H2O –> 2H+ + Cl- + ClO-
(Reversible)

27
Q

What is a disproportionation reaction?

A

One where the same species is both oxidised and reduced simultaneously

28
Q

Why is the reaction of chlorine and water without UV a disproportionation reaction

A

Cl2 is both oxidised and reduced

29
Q

Which species is oxidised and which species is reduced in the reaction of chlorine and water without UV

A

Cl2 is reduced and oxidised

30
Q

What is the benefit of adding Cl2 to water

A

Cl2 kills microorganisms

31
Q

What is the risk of adding cl2 to water

A

Cl is toxic to humans in large amounts

32
Q

What is the equation for the reaction of Cl and water with UV

A

2Cl2 + 2H2O —> 4HCl + O2

Ionic:
2Cl2 + 2H2O —> 4H+ + 4Cl- + O2

33
Q

Which species is oxidised and which species is reduced in the reaction of chlorine and water with UV

A

2Cl2 is Reduced

2H2O is Oxidised

34
Q

What is the chemical formula for bleach

A

Sodium Chlorate(I)

NaClO

35
Q

What is the equation for the manufacture of bleach

A

Cl2 + 2NaOH –> NaCl + NaClO + H2O

Ionic:
Cl2 + 2OH- —> Cl- + ClO- + H2O

36
Q

Which species is oxidised and which is reduced in the reaction for the manufacture of bleach

A

Cl2 is oxidised and reduced

37
Q

What type of reaction is the manufacture of bleach

A

Disproportionation

38
Q

State the colours of precipitate formed when AgNO3 is added to Cl-,Br-, and I-

A

Chloride (Cl-) ions: Produce a white precipitate of silver chloride
Bromide (Br-) ions: Produce a cream precipitate of silver bromide
Iodide (I-) ions: Produce a yellow precipitate of silver iodide

39
Q

Identify all the reduction products formed when solid sodium iodide reacts with concentrated sulphuric acid.

A

SO2
S
H2S

40
Q

Write the 3 redox equations after the initial reaction between NaI and H2SO4

A

HI
The initial reaction is NaI (s) + H2SO4 (aq) → HI (g) + NaHSO4 (s)

I2
Concentrated sulfuric acid can oxidize HI to iodine (I2), which appears as a violet or purple vapor: 2HI (g) + H2SO4 (aq) → I2 (g) + SO2 (g) + 2H2O (l)

S
Concentrated sulfuric acid can oxidize HI to sulphur (S), which appears as a yellow solid: 6HI (g) + H2SO4 (aq) → 3I2 (g) + S (s) + 4H2O (l)

H2S
Concentrated sulfuric acid can oxidize HI to hydrogen sulphide (H2S), which has a strong odour of bad eggs: 8HI (g) + H2SO4 (aq) → 4I2 (g) + H2S (s) + 4H2O (l)

41
Q

What is the half equation for so42- to SO2

A

SO42- + 4H+ + 4e- —> SO3 + 2H2O

42
Q
A

Chemistry (Inorganic) (7 decks)

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